1. Field of the Invention
The present invention relates to a laminated structural body having unidirectionally arranged strands sandwiched between two web layers such as of nonwoven fabric or film, and a method of and an apparatus for manufacturing such a laminated structural body.
2. Description of the Related Art
Various composite sheets of nonwoven fabric and resilient body have heretofore been proposed in the art. See, for example, Japanese Patent Laid-Open Publications Nos. 174764/96, 132856/97, 279453/97, and 222759/99. Japanese Patent Laid-Open Publication No. 174764/96 discloses a composite body comprising at least two laminated layers including a stretched long fiber web of thermoplastic resin and a stretchable elastomer layer, the composite body being stretchable in a limited direction. The stretched long fiber web comprises a unidirectionally stretched web of long fibers formed by spinning a thermoplastic resin, the long fibers being unidirectionally arranged.
Japanese Patent Laid-Open Publication No. 132856/97 reveals an extensible spun bonded nonwoven fabric which can be extended readily in the transverse direction under very small stresses and has an excellent surface strength and touch. To form the disclosed extensible spun bonded nonwoven fabric, a thermoplastic resin is melted and extruded into a group of continuous fiber filaments which are taken up while being stretched with a high-speed, high-pressure air stream by an ejector, opened, and caught and stacked on a catching support, thereby forming a web. Regular intermittent first self-fusion zones are formed in the web, thereby forming a continuous fiber spun bonded nonwoven fabric. There is longitudinally drawn the continuous fiber spun bonded nonwoven fabric having the first self-fusion zones such that the width of the nonwoven fabric before it is stretched and the width of the nonwoven fabric after it is stretched have a ratio ranging from 100:90 to 100:50. While the width of the nonwoven fabric after it is stretched is being maintained, the nonwoven fabric is heated by a heating roll to form regular intermittent second self-fusion zones. Specifically, after a spun bonded nonwoven fabric is lightly embossed, it is longitudinally stretched to reduce its width, and then further embossed.
Japanese Patent Laid-Open Publication No. 279453/97 shows a unidirectionally stretchable nonwoven fabric and a method of manufacturing such a unidirectionally stretchable nonwoven fabric easily and efficiently. According to the disclosed method, a nonwoven fabric made mainly of fibers of thermoplastic resin is produced. Then, the nonwoven fabric as an un-stretched raw fabric is uniaxially stretched at a temperature which is 60xc2x0 C. to 10xc2x0 C. lower than the melting point of the thermoplastic resin, by two nip rolls at a stretching ratio ranging from 1.4 to 4.0, the nip rolls being spaced in the stretch direction by an interval that is 0.5 to 10 times the width of the stretched raw fabric. In this manner, the unidirectionally stretchable nonwoven fabric is manufactured.
Japanese Patent Laid-Open Publication No. 222759/99 discloses a composite stretchable nonwoven fabric comprising a laminated structure of a stretchable nonwoven fabric of long fiber filaments and an extensible elastomer layer. The stretchable nonwoven fabric comprises a nonwoven fabric that is stretched at least three times in at least one direction. The stretchable nonwoven fabric is chiefly made of long fiber filaments each having a diameter ranging from 3 xcexcm to 15 xcexcm, and can be spread at least 150% without a reduction in elongation stresses when elongated in a direction perpendicular to the stretch direction. The elastomer layer may be in the form of a film, a nonwoven fabric, a foamed body, or the like. The elastomer layer and the stretched nonwoven fabric are joined to each other by an extrusion lamination process, a bonding process using an adhesive, or a process of applying an elastomer solution.
Apparatus for manufacturing a web by spinning strands with a rotating spinning head are disclosed in Japanese Patent Publications Nos. 60462/82, 35301/82, 39539/84, and 52228/85. For example, Japanese Patent Publication No. 39539/84 discloses a manufacturing apparatus which ejects a melted polymer under centrifugal forces from the spinning nozzles of a spinning head that is rotating at a high speed. The ejected filaments of the melted polymer are cooled and solidified by a cylindrical cooling surface disposed around the spinning head. The material of the filaments, i.e., the material polymer, mainly comprises a thermoplastic polymer. To the cooled and solidified filaments, there is bonded a pair of warp selvedge members extending substantially perpendicularly to an arranging direction of the filament, thus producing a parallel weft body composed of filaments bonded to the warp selvedge members.
When a composite sheet is manufactured as a laminated body of a nonwoven fabric and a resilient body, the resilient body and its material are handled in an exposed state in a certain process. In such a process, the material of the resilient body adheres to components of the manufacturing apparatus, thus blocking the manufacturing apparatus, and depositing the resilient body on components of the manufacturing apparatus. Therefore, the manufacturing apparatus tends to have mechanical problems. The manufacturing apparatus disclosed in Japanese Patent Publication No. 39539/84 also has a process of solidifying filaments spun by a spinning head with a cooling surface and a process of transporting the filaments in an exposed state. Therefore, since the material of the resilient body is liable to adhere to components of the manufacturing apparatus, the manufacturing apparatus tends to be blocked, and the resilient body tends to be deposited on components of the manufacturing apparatus.
It is therefore an object of the present invention to provide a laminated structural body of a web as of nonwoven fabric and resilient strands laminated on the web, which laminated structural body can be manufactured industrially efficiently by preventing a manufacturing apparatus from being blocked due to the adhesion of the material of the strands to components of the manufacturing apparatus and also preventing the material of the strands from being deposited on components of the manufacturing apparatus, and a method of and an apparatus for manufacturing such a laminated structural body.
To achieve the above object, there is provided in accordance with the present invention a laminated structural body of a web shape comprising a laminated body with a layer of strands laminated on the inner surface of a tubular nonwoven fabric, the laminated body being folded flatwise, the strands being arranged transversely of the laminated structural body between folded layers of the nonwoven fabric. The strands which are unidirectionally arranged are sandwiched between two layers of the nonwoven fabric, and covered in their entity with the nonwoven fabric. Preferably, the strands are made of a thermoplastic elastomer, and the nonwoven fabric has an elongation of 100% or higher in the transverse direction of the laminated structural body. For example, the tubular nonwoven fabric has high strength in the longitudinal direction thereof and an elongation of 100% or higher in the transverse direction of the laminated structural body, and the strands have large stretchability. The laminated structural body is longitudinally highly strong and dimensionally stable, and transversely highly stretchable. To manufacture such a laminated structural body, a nonwoven fabric is curved into a cylindrical shape, and strands are spun in the cylindrical nonwoven fabric and laminated on an inner surface of the cylindrical nonwoven fabric. A laminated body, which comprises the cylindrical nonwoven fabric with the strands laminated on the inner surface thereof, is folded flatwise into a laminated structural body. In the manufacture of the laminated structural body, any process in which the material of the strands is handled in an exposed fashion and any process in which the strands are delivered in an exposed fashion are very short. Therefore, a manufacturing apparatus is prevented from being blocked due to the adhesion of the material of the strands to components of the manufacturing apparatus, and the material of the strands is prevented from being deposited on components of the manufacturing apparatus.
A method of and an apparatus for manufacturing a laminated structural body produce a laminated structural body of the above structure, i.e., a laminated structural body having two web layers with unidirectionally arranged strands sandwiched therebetween. According to the method and the apparatus, a cylindrically curved web is delivered in a direction parallel to a central axis thereof in a state where the web is kept in a cylindrical shape, and a polymer liquid is discharged from a spinning head, which is disposed in the cylindrical web and rotated about the central axis of the cylindrical web, toward an inner surface of the cylindrical web to spin strands of the discharged polymer liquid and laminate the strands, which are arranged in a direction substantially parallel to the circumferential direction of the cylindrical web, on the inner surface of the cylindrical web. In this manner, the strands arranged substantially uniformly on the inner surface of the cylindrical web are laminated on the web, and joined to the web Then, the cylindrical web with the strands laminated thereon is sandwiched between a pair of pinch rollers, for example, so as to be folded flatwise to sandwich the strands between the two folded layers of the web. In this fashion, the laminated structural body having two web layers with unidirectionally arranged strands sandwiched therebetween is manufactured. According to the method and the apparatus, it is possible to manufacture the laminated structural body industrially efficiently. In the method and the apparatus, any process in which the material of the strands is handled in an exposed fashion and any process in which the strands are delivered in an exposed fashion are very short. Therefore, if the strands which are sticky are used as an intermediate layer of the laminated body, then the manufacturing apparatus is prevented from being blocked due to the adhesion of the material of the strands to components of the manufacturing apparatus, and the material of the strands is prevented from being deposited on components of the manufacturing apparatus. Consequently, the laminated structural body can be manufactured at a rate greater than the production rates of the conventional processes.
The term xe2x80x9cstrandsxe2x80x9d used herein includes a relatively thin endless or nearly endless flexible material usually referred to as filaments, and also a relatively thick endless or nearly endless flexible material. Filaments have a thickness of at most about several hundred tex., and strands have a thickness of up to about several thousand tex.
In the description of the present invention above and below, the term xe2x80x9celongationxe2x80x9d is in conformity with JIS (Japanese Industrial Standard)-L1095. That is, a web of a width of 5 cm is held so as to extend over a distance of 10 cm in the longitudinal direction and elongated at a velocity of 30 cm/min. Then, the rate of elongating length to its original length upon breaking the web is expressed in a manner of %.
The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.